Definitive Answers to your questions will be difficult.    I have had a few in rimfire cals (.22lr, 4mm Zimmerstutzen). Emailed the Weihrauch factory years ago and nobody there knows.  All the skilled craftsmen that worked these beauties left/retired in the mid to late 1970's. 

I cannot locate me Advert from the 1950's, however if I recall the only CF caliber was .22 hornet (?).  You may want to search if I posted one of those Advert here years ago?   I know they had 1 CF caliber along with .22lr and 4mm Zimmerstutzen. 

If your thinking of making it into a 8.15x46R you can forget about that.   I researched that and had a well known smith check the receiver walls and they're too thin.   Also the metal used in the beginning (the line was started in 1952 after the war that devastated the German industry) was weak and inferior early on.   Not saying it didn't improve over the years, it did, just saying early on the metal was weaker.

And yes there is a different firing pin and block between RF and CF.

Hope this helps
Chuck

I saw one a few months back chambered in 8,15x46R but it was a first and last time. They are fairly common here in Germany in 22 Hornet.